FIGS. 8A and 8B are sectional views showing a state where a conductor crimping portion 512 of a general crimping terminal is swaged to a conductor W of an electric wire (for example, refer to Patent Document 1).
In general, the conductor crimping portion 512 of the crimping terminal is formed into a substantially U-shaped section with a slightly bent bottom plate 521 by the bottom plate 521 and a pair of conductor swage pieces 522, 522 that extends upward from both left and right edges of the bottom plate 521, is rolled inward to wrap the conductor W of the electric wire placed on an inner surface of the bottom plate 521 and is swaged so that a leading end thereof is bitten to the conductor W, respectively.
Since the crimping terminal is mounted on a vehicle, the crimping terminal should sufficiently bear thermal impact. For example, in a sampling evaluation test, the conductor crimping portion 512 is continuously applied with repeating stress of high (about 120 degrees) to low (normal temperature) temperatures, as the thermal impact.
The solid line of FIG. 8A indicates a deformed shape at high temperature and the broken line indicates a deformed shape at low temperature. Also, the solid line of FIG. 8B indicates a deformed shape at low temperature and the broken line indicates a deformed shape at high temperature.
Like this, as the environmental temperature continuously repeats between the high and low temperatures, the conductor crimping portion 512 repeats expansion as shown in FIG. 8B and contraction as shown in FIG. 8B, as if it respires. However, in some terminals, it was found that a contact resistance between the conductor and the terminal is increased as the thermal impact is repeated.
Studying on the cause, it was found that the terminal (conductor crimping terminal 512) covering the conductor W from the outside may slightly move relative to the conductor W during the repeating thermal expansion and thermal contraction and the crimping performance may be thus highly lowered. In particular, analyzing the movement of the conductor crimping portion 512, it was understood that bending deformation of the bottom plate 521 about a central portion G in a width direction of the bottom plate 521 of the conductor crimping portion 512 or movement of parts extending from the bottom plate 521 to the conductor swage pieces 522 is important. Based on this, it was found that when the part extending from the bottom plate 521 to the conductor swage pieces 522 is highly deformed, a high influence on the contact resistance between the conductor W and the terminal is apt to occur.